This invention relates to a multiple spindle machine having a first variable speed motor for the spindle drive and and a second variable speed motor coupled to the camshaft for the tool feed drive.
A multiple spindle machine comprises an array of tools which perform sequential operations on a plurality of workpieces supported by a circular array of spindles. Means are provided for rotating the individual spindles and the entire spindle assembly, and a separate machining or forming operation is performed on a workpiece at each one of a series of spindle stations.
In machines such as this, power is required (1) to rotate the individual spindles, (2) to rotate or index the spindle assembly around the assembly axis, and (3) to feed tools into contact with the workpiece at the various spindle stations in order to machine the workpiece into the desired finished product.
In most prior art machines, a single constant speed motor is the only motive source for the entire machine. The motor is coupled through a transmission which provides the power to rotate the individual spindles. The motor also provides the power through a camshaft to advance and retract the tools with respect to a workpiece and to rotate or index the spindle assembly around its axis. All functions of the machine are interrelated by the various gears and cams used in the machine. This keeps all functions of the machine in synchronism, resulting in long-term trouble-free operation.
Multiple spindle machines are ideally suited for production runs involving many thousands of identical pieces. Such machines have the disadvantage, however, of requiring the gears, cams, and tools to be changed when there is any change to the geometry of the finished part. The gears must also be changed when it is desired to change the rotational speed of the spindles, or the speed of the camshaft which drives the tools. Changing the gears and cams often takes several days on a prior art machine.
In order to make multiple spindle machines more flexible, it is also known to use a spindle motor to drive the spindles but to eliminate the camshaft and provide separate numerically controlled (NC) motors for actuating all motions of the tools. In this way, changes in tool motion can be made by changing the program controlling the NC motors which actuate the tools. While this system is more flexible, there are several disadvantages: 12 to 15 NC motors are required, NC motors are expensive to manufacture and are prone to malfunction, the program needed to control 12 to 15 NC motors is extremely complex, and NC motors typically do not provide as much torque to feed the tool into the workpiece as does the camshaft in a conventional multiple spindle machine.
It would, therefore, be desirable to provide a multiple spindle machine having greater flexibility than normal prior art camshaft machines but without the disadvantages associated with a fully numerically controlled multiple spindle machine.